Galactic Survivors
Game
Galactic Survivors is a survivors-like that runs in a browser: you land on an alien planet, survive twelve minutes of its native creatures, and then fight the hive's Matriarch. It started from a recorded conversation between two players of Vampire Survivors and Halls of Torment, who talked through what makes these games work while they played. I read the transcript for those points and turned each one into a rule the game enforces and a test checks.
Moment to moment, the whole job is moving. Your abilities aim and fire on their own, and the camera never turns or shakes. An enemy can hurt you at most once in a short window, so a crowd pressed against you lands one hit, and no enemy is immune to anything.
Abilities are built as well as picked, after the wands in Noita. Each ability slot is a rig, a row of sockets read left to right, and level-up cards offer parts to put in it. A modifier changes the next ability, a formation fires it several times, and a trigger fires the rest of the rig where that ability hits, ends or defeats an enemy. Some abilities leave fire, frost, charge or slick on the ground, and two fields that meet react. Walking a closed loop draws a rune, which strikes everything inside it and gives a passive for a while.
Between runs you keep your gold and spend it on permanent upgrades, and achievements open those upgrades one rank at a time. The 64 achievements sit on a grid where earning one shows its neighbours. Tickets from bosses, rifts and achievements buy modules and rare parts in a salvage cache, with the odds on the screen.
Two players can play the same run, each in their own browser, joined by a room code or a pasted invitation. Each browser runs the whole run and sends only its key presses. Your own moves show at once, and your partner's are predicted and corrected when their keys arrive. Every rule runs in a Rust core in integer maths, compiled to WebAssembly, and the art is drawn in TikZ.
Playing it
WASD or the arrow keys move, and the mouse aims the few abilities that use it. Press 1, 2 or 3 to choose a level-up card, E to open your rigs, Space to dash as Vector, and Esc to pause. Your progress is a file: after a run, download your save, and load it next time. The page keeps nothing in your browser.
Checked in Chromium, Firefox and WebKit.